Abdominal pain is the single most frequent complaint for patients seen in the emergency department. The evaluation of these patients frequently involves the use of medical imaging. Computed tomography (CT) is by far the most widely used imaging modality for this indication, but exposes patients to levels of radiation that put them at risk for developing cancer. The intravenous contrast agent used for CT scans is also known to cause kidney injury, leading to dialysis and even death. Alternative imaging tests, including magnetic resonance imaging (MRI) and ultrasound (US), have high accuracy for detecting emergent causes of abdominal pain and do not expose patients to cancer-causing radiation nor kidney damaging contrast agents. Though guidelines advocating the use of US and MRI instead of CT exist, physicians are not routinely following them. This K08 proposal will evaluate the barriers and facilitators to the use of US and MRI in the emergency department. Dr. Repplinger is an Assistant Professor at the University of Wisconsin ? Madison, with a primary appointment in the BerbeeWalsh Department of Emergency Medicine and cross-appointment in the Department of Radiology. His research focuses on evaluating radiation-free imaging alternatives to CT, particularly the use of MRI. This line of investigation has been very successful due to the care he has taken in assembling and maintaining an interdisciplinary team of collaborators with expertise in medical physics, emergency care, radiology, and health services research as well as his unique qualifications. Support from this 3-year K08 award would provide Dr. Repplinger with the dedicated time needed to successfully complete his proposed research project. Further, he would be able to pursue career development activities that will significantly accelerate his progress toward becoming an independent investigator. The proposed aims are: 1) Identify high impact barriers and facilitators to guideline-adherent use of MRI and US in the ED; 2) Design a candidate intervention bundle targeted to high impact barriers and refine it using input from key stakeholders; and 3) Test the impact of the candidate intervention bundle on image test guideline adherence for pediatric appendicitis. These aims will be accomplished using a mixed-methods approach: qualitative analysis of focus groups for aims 1 & 2 and administrative data from our electronic health record for aim 3.